Its strongest growth was in its Liberalised Business sector, which soared by 187% to £271.8 million, recovering from a “difficult year” in 2017.

The bulk of the profits were achieved by the company’s household retail arm, which maintained customer numbers above five million through the period.

Keith Anderson, CEO of ScottishPower, said: “Last year was a pivotal year for ScottishPower as we completed the landmark journey from coal and gas to 100% green power by selling our generation business.

“ScottishPower has changed and we are proud to be different to others in our sector. It’s clear our customers are backing our commitment to green energy and our investment in a cleaner healthier future as, unlike others, our overall customer numbers have remained stable in 2018.”